The disorder broke out in F Wing at the Category B prison, which has a capacity of 888 prisoners and is run by private firm Serco.
Staff lost control of the wing at around 5.40pm this evening after being chased off by convicts carrying knives, according to reports.
Guards are believed to be awaiting the arrival of riot police to stem the trouble.
An anonymous inmate at Lowdham Grange said the violent scenes had been sparked by a row over the prison’s conditions.
He added: “They’ve taken control of F Block. They’re armed with knives and weapons.
“The prison officers were chased off the wing at around 5.40pm, and we’ve been in lockdown since 6pm.”
A Serco spokesman said: “We can confirm that there is an incident of concerted indiscipline at HMP Lowdham Grange.
“The incident involves a handful of prisoners and contained within one wing. We are working to resolve the incident as soon as possible.”
It is thought there are nearly 70 prisoners in the affected wing of the prison.
Lowdham Grange, which opened in 1998, is a training prison for men with sentences of at least four years.
It is run by Serco on behalf of the Ministry of Justice under a controversial outsourcing contract.
The prison, located in the Nottinghamshire village of Lowdham, is around 11 miles from Nottingham city centre.